1. Field of the Invention
The present invention relates to a method for controlling a spindle-drive type yarn winder.
2. Description of the Related Art
Recently, when a synthetic fiber yarn is continuously taken up at a high speed, a spindle-drive type yarn winder is used, comprising a turret member on which a plurality of spindles are rotatably mounted, a traversing mechanism held on a machine frame to be located upstream of one spindle which is in a yarn winding condition, a contact roller to be brought into press-contact at a predetermined pressure with a yarn layer wound on a bobbin carried on the spindle, induction motors for driving each one of the spindles, an induction motor for driving the contact roller, an inverter for controlling the rotational speed of each induction motor, and a controller for controlling the rotational speeds of each one of the spindles and the contact roller.
The yarn winder of the above-mentioned type is disclosed, for example, in Japanese Unexamined Utility Model Publication No. 5-27404, wherein the rotational speeds of the contact roller and the spindle in a normal winding mode are controlled in a different manner from that in a yarn switching mode by detecting the rotational speed of the contact roller, so that the circumferential speed is always constant by driving the contact roller at a predetermined rotational speed.
In such a method for controlling the surface speed of the contact roller at a constant value as stated above, there is a drawback in that yarn properties such as a stretch tension value, a thermal contraction stress value or the like in the innermost layer of a yarn package, which is formed in the yarn switching mode, deteriorate compared to those in the intermediate layer of a yarn package, which is formed in the normal winding mode.
It is surmised that the above change of yarn quality is caused by the actual increase of yarn tension in the yarn switching mode.